USB speakers not working

I just installed a pair of Logitech USB speakers to my laptop (Vista). As expeckted, my laptop speakers now don't work, but neither do the ISB speakers. I've checked all possible MUTE controls and all are off. Using Control Panel>Sound>Playback, I've set the USB speakers as the default. Using the TEST and CONFIG, no tones are going to the speakers. I've tested the speakers on another computer and they work fine. Can someone please tell me what setting I'm missing? PROBLEM UPDATE: By chance I have now noticed that the speakers work just fine if I RESTART my computer. They do not work if I come from HIBERNATION!

Here is an update for all readers. This problem apparently is another of the wonderful woes of Vista. Check out this bulletin: http://support.microsoft.com/kb/933262